WASHINGTON – President Barack Obama vowed Wednesday the United States would "work with the Libyan government to bring to justice" those who killed U.S. ambassador Chris Stevens and three other American personnel in an attack on the consulate in Benghazi.

"Make no mistake. Justice will be done," he said in an appearance at the Rose Garden outside the White House.

Obama, who ordered an increase in security at U.S. facilities overseas, said he "condemns in the strongest possible terms the outrageous and shocking" attack. He spoke after Republican presidential challenger Mitt Romney condemned the attack, and criticized the administration for its initial response to a separate incident on Tuesday, the breach of the U.S. embassy in Cairo.